The Neurology of Memory & Anterograde and Retrograde Amnesia
Memory is defined as “the mental capacity to encode, store, and retrieve information” (American Psychological Association, 2002). It is a part of the means by which humans function. The process of forming and recalling memories involves various complex neurological processes and disruptions to these processes can result in loss of memory or the inability to form new memories. Amnesia is a memory disorder, in which, due to trauma or a head injury, certain parts of the memory is inaccessible. The two main types of amnesia are anterograde amnesia and retrograde amnesia. Anterograde amnesia refers to the inability to create new memories (Mastin, 2010). “Retrograde amnesia refers to loss of memory for information acquired before the onset of amnesia” (Squire & Alvarez, 1995, p. 169).
The aim of this report is to explore the neurology of memory, and the processes of encoding, consolidation, storage and retrieval as well as briefly investigate the two main types amnesia, anterograde and retrograde amnesia.
Neurons and Memory
The average brain has around a 100 billion electrically excitable neurons and these are the cells involved in the encoding, consolidation, storage and retrieval of memory (Mastin, 2010). Neurons use electro-chemical signals to process and transmit information. Neurons maintain voltage gradients across their membranes, driven by differences of ion concentrations of sodium, potassium, chloride and calcium within the cell, which each contain different charges (Mastin, 2010). An electrochemical impulse called an action potential is generated when this voltage gradient changes significantly (Mastin, 2010). This pulse travels quickly along the cell's axon and is transferred to a neighboring neuron through the synapse via neurotransmitters (Mastin, 2010). These neurotransmitters are chemical messengers that relay, amplify and modulate signals between neurons (Mastin, 2010). Neurons are released by axon terminals in response to electrical impulses and they cross the cell membrane into the synaptic gap between the neurons (Mastin, 2010). These neurotransmitters bind in the chemical receptors of the dendrites of the post-synaptic neuron (which will receive the signal) and in doing so, open up specific ion channels to let in certain charged ions (Mastin, 2010). This alters the voltage gradient of the post-synaptic neuron and thus creates an action potential (Mastin, 2010). In this way, each neuron processes and transmits information and forms thousands of links with other neurons (Mastin, 2010). With each new experience or remembered event, the brain slightly rewires its physical structure. Neural networks are formed when functionally related neurons connect to each other (Mastin, 2010). These connection grow stronger as more signals are sent between them and the response of the post-synaptic neuron increases in amplitude (Mastin, 2010). This is because when a...